The invention is related to the field of photodynamic therapy (PDT), and in particular to a light delivery device (LDD) used in PDT.
In the medical device field there are numerous techniques to deliver light to perform a medical procedure, but the two most common techniques are direct and focused illumination. Direct illumination occurs with a bare or diffused light source placed a distance of several centimeters to meters from the patient. Direct Illumination devices are rarely attached to the patient. In general, the patient is required to position themselves to the illumination source. Examples of light delivery devices that fall within this category include conventional phototherapy units, such as the standard light box and hand/foot units that emit UV-A, UV-B or narrow-band UV-B light.
Phototherapy units are used primarily for the treatment of inflammatory skin diseases such as psoriasis. The units are also used in conjunction with orally or topically administered psoralens that photoactivate with UV-A light in the treatment of severe psoriasis and extensive vitilligo. This treatment is known as PUVA (psoralen UV-A) therapy. For systemic diseases such as cutaneous lymphoma, graft versus host disease and systemic sclerosis, extracorporeal photophoresis is performed where the patient ingests the psoralen and the blood is exposed to the UV-A light outside the body and then re-infused into the patient. The DUSA (blue visible light) and Galderma-Metvix (red visible light) systems are used for the treatment of actinic keratoses (pre-malignant skin growths) and superficial basal cell carcinomas. They work via topical aminolevulinic acid (DUSA) and methyl-aminolevulinic acid PDT.
Focused illumination, both internal and external to the patient treatment site requires illumination that has an optical system to direct light from the illumination device to specific areas onto the patient, typically in a controlled beam shape and beam intensity. In many cases the optical system is composed of one or more optical fibers that use total internal reflection to collect light at one end of the fiber, transmit the light, and exit with a specific numeric aperture at the other end. Typically this approach requires larger fibers or an array of large fibers to illuminate large areas (>5 mm). Illuminating more than a single fiber requires sophisticated coupling of the light into the fibers. This coupling is usually inefficient and can have very low coupling efficiency (<10% efficiency). Similar to direct illumination, the focused illumination approaches are rarely done where a patient wears a device.
For FDA approved PDT indications, there are numerous light illumination devices meeting the direct and focused illumination schemes. For example, for Barrett's esophageal cancer treated with PDT, a focused illumination system is implemented using a fiber optic cable attached to a FDA approved laser system such as the Angio Dynamics PDT 630 nm laser. Alternatively, a direct illumination approach to PDT for actinic keratosis is done using similar devices such as DUSA's Blue-Light Phototherapy Lamp or Galderma's Aktilite which is also used for basal cell carcinoma skin cancer.
There are few wearable medical based illumination devices except for the Ambicare Health Ambulight PDT device that only covers a small area and has no degree of flexibility or conformity to anatomical features. The device is a pad of LEDs that are placed directly on the treatment area. This method of delivery does allow the system to be portable, but it places the illumination source directly on the patient causing thermal side effects.
Another device that is wearable, but displaces the illumination source and any generated heat from the source at a distance from the treatment site is a weaved collection of fiber optic cables that are bent sharply at several locations along the length of the fiber. The bending of the fiber cause light to leak from the fiber illuminating a small portion of a light illumination surface that consists of hundreds to thousands of these bent fibers. This weaved fiber approach provides imprecise quantities of light at the treatment site because the bending (the mechanism of light leakage) of the fiber is not uniform from bend to bend and the location of bending along similarly aligned fibers can be random from fiber to fiber.